1. Field of the Invention
The present invention relates to drums such as bass drums, snare drums, and marching drums.
The present application claims priority on Japanese Patent Application No. 2007-138995, the content of which is incorporated herein by reference.
2. Description of the Related Art
Drums such as bass drums, snare drums, and marching drums are each formed using a drum shell having a cylindrical shape having openings at both ends, across which drumheads are stretched under tension. When a drum is struck with a drumstick, primary sound is produced due to an impact between the drumstick and the drumhead. In a drum shell having opposite openings, across which first and second drumheads are stretched under tension, when the first drumhead is struck with a drumstick, vibration occurs by the first drumhead and is transmitted to the second drumhead by way of air inside of the internal hollow space of the drum shell, whereby the second drumhead vibrates so as to cause further vibration, which is then transmitted to the first drumhead. Therefore, the first and second drumheads repeatedly vibrate via air in the internal hollow space, thus producing secondary sound. For this reason, drum playing is realized by way of the primary sound due to an impact between the drumstick and drumhead and the secondary sound due to vibrations repeatedly transmitted between the first and second drumheads.
Conventionally, various types of drums have been developed and disclosed in various documents such as Patent Document 1 to Patent Document 4.                Patent Document 1: Japanese Unexamined Patent Application Publication No. H08-6547        Patent Document 2: U.S. Pat. No. 4,300,437        Patent Document 3: U.S. Pat. No. 4,060,019        Patent Document 4: Japanese Unexamined Patent Application Publication No. 2001-318667        
FIG. 5 shows a conventional example of a snare drum 1, which includes a drum shell 2 having a cylindrical shape (having openings at both ends) and drumheads 3 that are stretched under tension uniformly applied thereto at the openings of the drum shell 2 and are supported by a drumhead support device 4.
The drum shell 2 can be composed of wooden materials, fiber-reinforced plastics (FRP), and metals, for example. It is required that the shape of the drum shell 2 be stably maintained irrespective of weather conditions and variations of tensions applied to the drumheads 3, it be formed to prevent bad tuning, and it be formed to prevent self-vibrations or self-sound-absorption.
The drumhead 3 can be formed using natural leather and synthetic resin films (composed of polyester resin, polycarbonate resin, etc.).
The drumhead support device 4 includes hoops 5 (see FIG. 2), which hold the peripheral portions of the drumheads 3 and which are engaged with the exterior surface of the drum shell 2 in proximity to its openings, clamp frames 6 engaged with the circumferential peripheries of the hoops 5, lugs 7 fixed to prescribed positions of the exterior surface of the drum shell 2, and tuning bolts 8 for interconnecting the clamp frames 6 and the lugs 7 together. When the user (or a player) rotates the tuning bolts 8 using tuning keys (not shown) so as to move the clamp frames 6 in axial directions, depressions of the clamp frames 6 applied to the hoops 5 vary so as to adjust tensions of the drumhead 3, i.e., to adjust the tone color of the snare drum 1. Reference numeral 9 designates a snappy member consisting of snares; and reference numeral 10 designates strainers for moving the snappy member 9 to come in contact with or separate from the drumhead 3.
There are two types of snare drums each having two drumheads, i.e., a first type of snare drum that has an air hole 11, i.e., a vent hole allowing the exterior surface and the interior wall of the drum shell 2 to communicate with each other, and a second type of snare drum that does not have the air hole 11. In the second type of snare drum not having the air hole 11, air pressure inside of the drum shell 2 may rapidly increase when the drumhead 3 is struck with a drumstick, so that acoustic waves occur due to the displacement of the drumhead 3 and intensely interfere with acoustic waves that are reflected at the backside of the drumhead 3, thus decreasing the volume of drum sound. The second type of snare drum suffers from slow damping of vibration; hence, it cannot produce a sharp drum sound.
In the first type of snare drum (i.e., the snare drum 1 having the air hole 11), it is possible to prevent air pressure inside of the drum shell 2 from rapidly increasing due to the air hole 11, thus weakening interference between acoustic waves; and it is possible to reduce resonating sound while securing an adequate volume of drum sound. In particular, the air hole 11 may prevent the sharpness of tone color from being degraded during a soft playing mode, in which the user softly strikes the drumhead 3 with a drumstick; and it may prevent the drumhead 3 from being accidentally destroyed in a hard playing mode, in which the user intensely strikes the drumhead 3 with a drumstick.
When the drumhead 3 of the snare drum 1 having the air hole 11 is struck with a drumstick, the drumhead 3 vibrates about the inside position of the drum shell 2 rather than the normal position of the drumhead 3 not being struck. This is because the displacement of the drumhead 3 due to striking occurs inwardly in the drum shell 2 so that air is discharged outside via the air hole 11, wherein the drumhead 3 vibrates based on the air pressure inside of the drum shell 2 below the atmospheric pressure. However, the vibration of the drumhead 3 cannot last stably, and loss of vibration energy is relatively high; hence, the vibration will be rapidly damped. This improves the sharpness of the drum sound compared with the drum sound produced by the first type of snare drum not having the air hole 11.
When air flow occurs from the outside to the inside via the air hole 11 of the drum shell 2, a rapid state transition occurs in a short time period with respect to the drumhead 3 from an unstable vibrating state to a stable vibrating state, offering a small energy loss (in which the drumhead 3 vibrates about the normal position thereof), wherein the vibration of the drumhead 3 is damped slowly; hence, it is difficult to produce an adequately sharp drum sound.
Patent Document 1 teaches a drum that is designed to solve the aforementioned drawback, wherein a check valve is attached to an air hole so as to restrict air flow from occurring only in a direction from the inside to the outside in a drum shell. The check valve blocks air flow in a direction from the outside to the inside in the drum shell; hence, it is possible to rapidly damp vibration of a drumhead, thus producing a sharp drum sound.
Patent Documents 2 to 4 teach drums whose tone colors can be varied. Patent Document 2 teaches a drum in which the depth of a drum shell is varied so as to vary air load in the drum shell, thus varying the tone color. Specifically, the drum shell is constituted of a top shell and a bottom shell that are divided in an axial direction and that are interconnected together to move close to or distant from each other. A gap is formed between the joint surfaces of the top shell and bottom shell as necessary so as to serve as an air hole. It also teaches another embodiment in which an intermediate shell is inserted between the top shell and the bottom shell, wherein gaps are formed among the top shell, intermediate shell, and bottom shell, and wherein screens for damping sound or for changing tone color are inserted into the gaps.
Patent Document 3 teaches a drum whose drum shell is constituted of two shells having different diameters, which are interconnected together via bolts so as to gradually adjust the lengths thereof, thus varying the depth of the drum shell.
Patent Document 4 teaches a drum whose drum shell is divided into first, second, and third shells that are divided in an axial direction, wherein the third shell is sandwiched between the first and second shells, and wherein drumheads are stretched across the openings of the first and second shells positioned relative to the third shell. Various sets of the first, second, and third shells are provided in terms of materials, structures, and depths and are selectively combined together so as to vary tone colors, tone pitches, low-frequency characteristics, and damping times.
The aforementioned drums disclosed in Patent Document 1 to Patent Document 4 have merits and demerits; hence, it is necessary to introduce further improvements on drums. In the drum disclosed in Patent Document 1, the check valve and a spring (for pressing the check valve to close the air hole) form a resonating system during play. In order to efficiently make air flow outside of the drum shell, it is necessary to precisely design the resonating system such that vibration pitches of the resonating system substantially match vibration pitches of the drumhead with respect to each type of drum. Hence, it is very troublesome in designing the check valve; this increases the number of check valves for use in different types of drums. The check value is provided outside of the drum shell; hence, it greatly degrades the exterior appearance of a drum.
In the drum disclosed in Patent Document 2, the top shell and the bottom shell are relatively interconnected to move close to or distant from each other by means of a slide mechanism. Similar to the drum of Patent Document 1, this drum is disadvantageous in that the slide mechanism, which is exposed outside of the drum shell, greatly degrades the exterior appearance thereof. When the top shell and bottom shell are moved close to or distant from each other so as to vary air load or air flow therein, the overall depth thereof is varied. In particular, the depth of a drum shell greatly affects performance of a drum; hence, it is inconvenient for the user to experience unexpected variations of the depth of a drum shell. In the foregoing drum in which a screen offering a damping effect or a screen for varying tone color is attached to the intermediate shell, it is very difficult to stably maintain the prescribed shape when the screen does not have a satisfactory degree of hardness; hence, there is a restriction in selecting materials for use in the screen. This drum is designed using two or three shells, which are interconnected together to move close to or distant from each other. That is, this drum structure may be suited to drums whose drum shells have relatively large depths, such as marching drums, whose drum shells generally have depths of about 12 inches. But it is not suited to other drums whose drum shells have relatively small depths, such as snare drums, whose drum shells generally have depths of about 5.5 inches.
Similar to the drum of Patent Document 2, the drum of Patent Document 3 is disadvantageous in that the depth of the drum shell thereof gradually varies.
The drum of Patent Document 4 suffers from drawbacks in custody, maintenance, and transportation because various types of shell members having different materials and structures must be provided therefor.